Attach parts to the top plate
Parts
Tools
Method
Prepare the standoffs
Insert a M3x6mm cap head screw into each standoff using the large hole that comes out the side of the standoff. When you are done, the screw should poke out the end of the part as shown. There should be four spacers, one for each corner of the plate. It's probably easiest to use a non-ball-ended hex key to put the screw into place, then use a 2.5mm ball-ended hex key to turn the screw. The hole may print a little tight - you can either clean it up with a 3mm drill, or simply turn the screw a few times before attaching it to the plate, to ensure any thread that might have formed is stripped away.
Attach the standoffs
Attach each standoff to one of the corners of the top plate.
Attach the focusing assembly
Using a M3x6mm cap head screw on either side of the focusing assembly, attach it to the top plate.
The top plate is now assembled, you can proceed to attach the bottom plate.